Sulfilimine compounds are of interest as intermediates in procedures for producing various o-alkylacetanilide compounds having herbicidal properties. Sulfilimines have previously been produced by reacting an aniline compound with dimethylsulfide in the presence of a source of positive chlorine, e.g. N-chlorosuccinimide. The N-phenyl-S,S-dimethylsulfilimine is then rearranged to an o-methylthiomethyl aniline, and the latter compound or derivative thereof is subjected to a reductive cleavage reaction to obtain an o-methylaniline. An electrolytic reductive cleavage reaction and further description of reactions leading to compounds with herbicidal properties is set forth in a commonly assigned copending application of Richard D. Goodin et al., Ser. No. 530,135, filed Sept. 7, 1983, and issued Jan. 15, 1985 as Patent No. 4,497,755 the disclosure of which is incorporated herein by reference. In the described procedures for producing sulfilimines it is necessary to have a source of positive chlorine, and it would be desirable to have a process which did not use such an agent and accompanying costs or need for recovery and regeneration procedures.
Certain activated isocyanate compounds have been reported to react with dimethyl sulfoxide at room temperature. Thus Arbuzov et al, Izv. Akad. Nauk. SSSR Ser, Khim, No. 5, pp. 1206-1207 (1975) states that trifluoroacetylisocyanate, as a strong electrophile, reacts with dimethyl sulfoxide to give N-trifluoroacetyl-S,S-dimethylsulfilimine, and C. King, J. Org. Chem. Vol. 25, pp. 352-356 (1960), shows conversion of p-toluenesulfonyl isocyanate to N-p-toluenesulfonyl dimethylsulfilimine.
Various aromatic isocyanates are reported to be produced by carbonylation of aromatic nitro compounds, generally at elevated temperatures and pressures with noble metal catalysts. The referred-to reports have not utilized the preparations in conjunction with reactions of the product with dimethyl sulfoxide to obtain sulfilimines, or with special compounds of interest for obtaining particularly desired products in the present invention, such as with o-nitro-trifluoromethylbenzene. U.S. Pat. Nos. 4,070,391 and No. 3,576,836 are among those describing carbonylation procedures in which aromatic nitro compounds are contacted at elevated temperatures and pressures with carbon monoxide in the presence of a noble metal catalyst, such as a palladium halide or a rhodium oxide. Such procedures, as well as those illustrated in the present specification, can be used in preparing isocyanates for conversion to sulfilimines in accord with the present invention. For example sub-atmospheric, atmospheric or superatmospheric pressures can be used, but elevated pressures are generally advisable to obtain good reaction rates with pressures generally in the range of about 500 to 10,000 psi (3447.5 to 68,950 KPa) and more commonly about 1500 to 5000 psi (10,342 to 34,475 KPa). Temperatures from ambient to 400.degree. C. can be used, depending on the catalyst, with some being conveniently used at about 100.degree. to 225.degree. C., while others are employed about 150.degree. to 225.degree. C. or higher.
Aniline compounds can be converted to phenylisocyanate compounds by reaction with phosgene, and this procedure can be utilized to obtain isocyanate compounds for further reaction herein. This can serve as an indirect route from nitrobenzenes to isocyanates herein, as nitrobenzenes are readily reduced, as by hydrogenation, to aniline compounds. Particular aniline compounds, e.g. ortho-trifluoromethylaniline, can be converted to phenyl isocyanate compounds under conditions generally known in the art for such conversion of other aniline compounds. For example, the aniline compound in solution in an inert solvent can be contacted with phosgene, possibly at low temperature to condense the phosgene, and then reacted further by moderate heating, to 100.degree.-150.degree. C. or so, with further addition of phosgene, or with use of pressure vessel to maintain some phosgene content in the solution.